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30 Cards in this Set
- Front
- Back
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Atoms radius and nucleus |
1 X 10^-10 (0.1 nano meters) Nucleus 1 X 10^-14 |
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What is an element |
If a substance contains only atoms with the same number of protons |
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What are isotopes |
Different forms of the same atom. They have the same atomic number but different mass numbers. They have more neutrons. |
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What is the formula for relative atomic mass (Ar) |
Sum of (isotope abdunace X isotope mass number) --------------------------------------------------------- Sum of abundance of all the isotopes |
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What are compounds |
Substances that are formed from two or more elements, they are of fixed proportion throughout the compound and are held by chemical bonds. |
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With ions wot do metals or non metals lose or gain |
Metal atoms lose electrons to form positive ions Non metal atoms gain electrons to form negative ions |
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What does a compound formed from non metals consist of |
Molecules. Each atom sharea electrons with another. This is covalent bonding. |
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State some ionic or covalent formulas |
Ammonia NH3 Calcium chloride CaCl2 Sodium carbonate Na2CO3 Sulfuric acid - H2SO4 |
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What are the propperties of a mixture |
A mixture of the propperties of the seperate parts |
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Describe chromatography |
A method of seperating substances in a mixture. Used to seperate different dyes in ink. Draw a line near bottom of a sheet of filter paper. Use pencil as it's insoluble. Add a spot of the ink to the line and place the sheet in a beaker of solvent e.g. water, but some substances may disolve better in other solvents e.g. ethanol. Make sure the ink isn't touching the solvent as it will dissolve it. Place a lid on top of container so the solvent doesn't evaporate. Each different dye will move up at a different rate so will seperate out . 1 spot per dye in the ink. If any of the dyes in the ink are insoluble they will stay on the baseline. When the solvent has nearly reached the top take the paper out and leave to dry. The point the solvent has reached as it moves up the paper is the solvent front. The end result is a pattern of spots called a chromatogram. |
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What is filtration |
Sepearating insoluble solids from a liquid reaction mixture. Filter paper is folded into a cone, the solid is left in the filter paper. |
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Way of sepearating soluble solids (soluble salt) from soloutions evaporation: |
Pour the soloution into a evaporating dish. Slowly heat the soloution with a Bunsen burner . The solvent will evaporate and the soloution will get more concentrated. Eventually crystals will start to form. Keep heating the evaporating dish untill all you have left are dry crystals. This can only be used of the salt doesn't decompose when it's heated, otherwise you have to use crystilation. |
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Ways of sepearating soluble solids (soluble salts) from liquids crystallisation: |
Pour the soloution into a evaporating dish and gently heat the soloution. Some of the solvent will evaporate and the soloution becomes more concentrated. Once some of the solvent has evaporated, or when you see crystals starting to form (the point of crystallisation) remove the dish from the heat and leave the soloution to cool. The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated soloution. Filter out the crystals from.the soloution and leave them in a warm place to dry e.g. a drying oven or a desiccator. |
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Describe simple distillation |
Used for sepearating out a liquid from a soloution. The soloution is heated. The part of the soloution that has the lowest boiling point evaporates first. The vapour is then cooled , condenses (turns back into a liquid ) and is collected. The rest of the soloution is left behind in the flask. You can use simple distillation to get pure water from sea water. The water evaporates and is condensed and collected. You will end up just the salt left in the flask. Simple distillation can only be used for things with very different boiling points. If the temp goes higher then both boiling points they will mix. So if you have a mixture of liquids with similar boiling points you use another method to seperate them , fractional distillation. |
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What is fractional distillation |
Used to seperate a mixture of liquids. Put your mixture in a flask and stick a fractional column on top. Then you heat it. The different liquids will all have different boiling points so evaporate at different temperatures. Liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid it will reach the top of the column. Liquids with higher boiling points might also start to evaporate but the column is cooler towards the top so they will only get part of the way up before condensing and running back down towards the flask. When the first liquid has been collected, you raise the temperature untill the next one reaches the top. Fractional column filled with glass rods Condenser is were the gasses condense into liquids Top part of column is coolest. |
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At the start of the 19th century |
John Dalton described atoms as solid spheres and said that different spheres made up different elements |
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In 1897 |
JJ Thomson said due to his experiments they weren't solid spheres. Stating that an atom contains even smaller negatively charged particles electrons. The new theory was the plum pudding model. He thought it was a ball of positive charge with negatively charged electrons in it. |
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In 1909 rutherford |
Lab scientists conducted the famous alpha particle scattering experiments. They fired positively charged alpha particles at an thin sheet of gold. They expected, due to plum pudding model, for the particles to pass straight through the sheet or be slightly deflected at most. As the positive charge of each atom was thought to be spread out in the plum.pudding model. But more then expected particles were deflected and some.were deflected backwards. This meant plum pudding wasn't right. Rutherford came up with the nuclear model. In this there's a tiny positively charged nucleus and a "cloud" of negative electrons surroundings so most of the atom is empty space. When alpha particles came near the concentrated positive charge of the nucleus they were deflected, or if they went directly at nucleus were reflected back. Otherwise they passed through the empty space. |
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What did Bohr do |
Scientists realised that electrons in a cloud around the nucleus of an atom, as Rutherford described, would be atracted to the nucleus and collapse. Niels Bohr nuclear model suggested that all electrons were contained in shells. He proposed that electrons orbit the nucleus in fixed shells and aren't anywhere in between. Each shell is a fixed distance from the nucleus. Bohr's theory of atomic structure were supported by many experiments and it helped to explain lots of other scientists observation at that time. |
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What happened after bohr |
Further experiments by Rutherford and others showed the nucleus can be divided into smaller particles, which have the same charge as a hydrogen nucleus. These were named protons. 20 years after scientists had accepted the nuclei James Chadwick carried out an experiment which provided evidence for neutral particles in the nucleus which are now called neutrons. The discovery of neutrons resulted in a model of the atom which was pretty close to the modern day accepted version , known as the nuclear model. |
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Early 1800s, what was periodic table like |
The elements were arranged by atomic mass. Their was only two obvious ways to categorise them, their physical and chemical.propperties and relative atomic mass. there was no such thing as atomic number to scientists then. Early periodic tables were not complete and some were placed in the wrong group. |
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What happened with periodic table in 1869 |
In 1869 Dimitri Mendeleev overcame early periodic tables problems by taking 50 known elements and arranging them with gaps . He put the elements mainly in order of atomic mass, but did switch the order if the propperties meant it should be changed. An example of this can be seen with Te and I - iodine actually has a smaller relative atomic mass but is placed after tellurium as it has similar propperties to the elements in that group. Gaps were left so elements with SIMILIAR propperties stayed in the same groups. Some gaps indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be. When these were found and fitted the pattern it helped confirm mendelevs ideas. |
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Describe the periodic table |
Elements with similar properties form columns. These vertical (going down ) columns are called groups. The group number shows the number of electrons on the outer shell. Group 1 elements react more vigorously as you go down the group and in group 7 reactivity decreases as you go down the group. Rows are called periods each new period represents another full shell of electrons. |
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Describe metals and non metals |
Metals are strong , malleable, great at conducting heat and electricity, have high boiling points and melting points. Non metals tend to be dull looking, more brittle aren't always solid at room temp don't generally conduct electricity and often have a lower density. |
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Describe group 1 elements |
They are reactive, soft metals. They have 1 electron in outer shell so have SIMILIAR propperties, very reactive . They are soft and have a low density . They are alkali. As you go down the group reactivity increases , boiling and melting point decreases and higher relative atomic mass. They form 1+ ions.its so easy for them to lose their outer electron that they only ever ready to form ionic compounds. These compounds are generally white solids that dissolve in water to form colour less soloutions. |
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What do group 1 metals do in water |
They react vigorously and produce hydrogen. They also form hydroxides that dissolve in water to give alkaline soloutions. |
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What happens when group 1 metals react with chlorine |
They react vigorously when heated in chlorine gas to form white salts called metal chloride. As you go down the reaction is more vigorous. |
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What happens when group 1 metals react with oxygen |
They form a metal oxide. Lithium forms lithium oxide( Li2O) Sodium reacts to form a mixcture of sodium oxide (Na2O) and sodium peroxide (Na2 O2) Potassium reacts to form a mixture of potassium peroxide (K2O2) and potassium superoxide (KO2) |
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Describe group 7 elements |
These are known as the halogens. They are all non metals with coloured vapours. Fluorine poisonus yellow Chlorine poisinose green Bromine poisonus red Liquid Iodine dark grey solid or purple vapor Exist as molecules.as you go down group 7 the halogens become less reactive, harder to gain an electron as the shel is so far from nucleus Higher melting points and boiling points Higher relative atomic masses. When halogens react with covalent bonds they form.simple mollecular structures. Most reactive halogens will displace less reactive ones. A displacement reaction can occur between a more reactive halogen and the salt of a less reactive one. |
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Describe group 0 elements |
Inert colourless gases. All have eight in their out shell apart from helium which has 2. Don't react much. Monatomic gasses , single atoms.not bonded. All.colourless gasses at room temp. They are non flammable. The boiling point of the noble gasses increase as you move down the group along with increasing relative atomic mass. Increase in boiling points is due to an increase in number of electrons and there is then stronger intermolecular forces. |
